Expected 50 for contest (4)
I believe the answer is:
duel
'for contest' is the definition.
(fight between two people)
'expected 50' is the wordplay.
'expected' becomes 'due' (similar in meaning).
'50' becomes 'l' (Roman numeral).
'due'+'l'='DUEL'
(Other definitions for duel that I've seen before include "Combat to settle a row" , "Fight between two persons" , "Single combat" , "Contest between two people, perhaps with weapons" , "Prearranged engagement" .)